I didn't even know they made these things until I was walking around the hardware store one time. I moved into a new house last year, and have been replacing a lot of the floors. When I moved in, there was a lot of worn and ugly carpet on the floors. Whenever I get it replaced, I always have to take off the trim from the bottom of the floor. Putting it back on afterwards is always a problem, because I can't figure out where I need to put the nails in.
Now that I have the stud finder, I can just run it along the wall and find where to put the nail in. It makes putting up the trim much faster and less frustrating.